1. Field of the Invention
The invention relates to a composite article which may be in rod, tube, strip, sheet or plate form and a process for its production into an article having reversible theremomechanical properties.
2. Description of the Prior Art
The so-called memory alloys belong to the materials that are distinguished by special thermomechanical properties deviating from normal behavior. Memory alloys include, among others, the alloys on Ni/Ti basis and the Cu alloys of the so-called .beta.-brass type to mention only the most important ones. Their compositions, properties and uses are known from numerous publications (Walter S. Owen, "Shape Memory Effects in Alloys," edited by Jeff Perkins, 1975, Plenum Press New York, Proc. of int. Symposium on Shape Memory Effects and Applications, Toronto, Canada, May 19-22, 1975).
The shape memory alloys are distinguished because their phase transition (transition from the martensitic to the austenitic structural arrangement and vice versa) generally occurs within a small temperature interval of a magnitude of 30.degree. C. This applies analogously also to the reversible shape changes connected with the transition regardless of their type and size.
In general, all temperatures for which shape changes are required cannot be carried out with a single shape memory alloy. Also, their thermomechanical properties are limited to a single type of deformation or to a single mode of movement in the transition range. Therefore there is a great need for materials which permit greater freedom to the design engineer in thermal as well as in mechanical characteristics.